Simulation Study On Resonant Characteristics Of Boron Nitride Carbon Nanotube Heterostructure

At present,nanoresonators have played an extremely important role in many domains such as mass detection.Especially,carbon nanotube(CNT)-based resonators have aroused widespread interest for their excellent mechanical properties and mass sensitivity.However,they have poor frequency self-tuning and require strong external drives and complicated calculation models to control the tuning range and accuracy.Recently,boron nitride nanotubes(BNNTs)have gradually attracted attention owing to their mechanical properties comparable to carbon nanotubes and unique piezoelectric tuning properties.It is,therefore,necessary to study the resonance characteristics of the CNT and BNNT coaxial heterostructure(CNT@BNNT),using the piezoelectric tuning property of the BNNT to solve the difficult tuning problem of the CNT.The piezoelectric tuning characteristics of CNT(5,5)@BNNT(17,0)and its application as a mass sensor are investigated by means of molecular dynamics simulations.Firstly,the variation of the resonant frequency of CNT(5,5)@BNNT(17,0)with the axial electric field is studied and compared with that of(17,0)BNNT and(5,5)CNT.The results show that the resonant frequency of CNT(5,5)@BNNT(17,0)has the same variation tendency as that of BNNT(17,0),though the variation amplitude of the former is smaller than that of the latter,while the resonant frequency of(5,5)CNT does not change.Further investigation shows that the axial mechanical deformation is generated in the(17,0)BNNT and CNT(5,5)@BNNT(17,0)by applying an axial electric field,which changes the axial load and ultimately affects their resonant frequency.In terms of energy dissipation,the variation of the quality factor with the axial electric field is similar to that of the resonant frequency.The analysis shows that the axial electric field changes the thermoelastic damping of(17,0)BNNT and CNT(5,5)@BNNT(17,0),thereby tuning their quality factor.In addition,the quality factor of CNT(5,5)@BNNT(17,0)is higher than that of(17,0)BNNT due to the weak van der Waals force and the mismatched interlayer lattice.After the piezoelectric tuning characteristics of CNT(5,5)@BNNT(17,0)are investigated,the application of CNT(5,5)@BNNT(17,0)as a mass sensor is further studied.The simulation results show that the mass resolution of CNT(5,5)@BNNT(17,0)increases with the increasing length.At different temperatures,the mass resolution of CNT(5,5)@BNNT(17,0)is basically stable,but the quality factor decreases with the increase of temperature,because the dissipation source such as thermoelastic damping increases with the increasing temperature,resulting in the reduced energy dissipation.In addition,the tuning effect of the axial electric field on the mass resolution of CNT(5,5)@BNNT(17,0)at different temperatures is mostly the same,but the tuning effect on its quality factor at low temperature is significantly better than that at high temperature.It is speculated that the thermoelastic damping and electron collision within the nanotubes at low temperature is lower than that at high temperature,so the tuning effect of the axial electric field is better at low temperature.In summary,the CNT(5,5)@BNNT(17,0)-based resonator studied in this paper can provide a theoretical basis for designing nanoresonators with excellent piezoelectric tuning properties and mass sensing performance.